Responses of plant stoichiometric niche to locust disturbance with different densities in Inner Mongolia grasslands

Abstract

Producers, consumers, decomposers and their relationships are all important biological components of a healthy ecosystem. Grasshoppers (including locusts) have been extensively studied as a group of members of grassland ecosystems. However, the effects of different degrees of locust disturbance on plant niches remain unclear. We carried out a field experiment by manipulating locust (Oedaleus asiaticus) grazing at different densities in the Inner Mongolia Grassland Ecosystem Research Station in northern China, to investigate the outcome of locust plague on plant C:N:P stoichiometric niche. Based on the Copula function with improved modelling methods to simulate the stoichiometric niche projection map of different plants, we found that Leymus chinensis and Stipa grandis, after being disturbed by locusts, had a relatively larger niche space and niche overlap among the seven plant species, indicating that they remained the dominant species in the area. Achnatherum sibiricum, Cleistogenes squarrosa, and Koeleria cristata showed little change in their C:N:P stoichiometric niche in response to locust plague, while the mechanisms involving stoichiometric niche variation were not the same in these plants; food importance to locust and physiology (e.g., photosynthesis pathway type) may account for this. Our results suggest that a heavy degree of locust plague might benefit the expansion of chemical niche space (species' niche in chemical resource utilization) in some plants in Inner Mongolian grasslands, but does not necessarily increase their physical niche (species' niche under abiotic environmental conditions like temperature and humidity). To our knowledge, the present work is the first to study C:N:P stoichiometric niche variation in response to locust disturbance and may have significance in theoretical studies and provide guidance for the protection of biodiversity and grassland ecosystem management.